~ Add a Little Reason to Your Day

Gravitational Lensing is the Coolest

Looking at the image below, you may think how cool the universe is to have a multi-core galaxy, but it’s an illusion. The universe is much cooler than that.

The Einstein Cross

It turns out that you aren’t seeing a galaxy at all, but most likely something behind it, like a quasar–the compact galactic cores that outshine nearly everything else in the universe.

A closer look at the Einstein Cross

But how could we be seeing something behind the galaxy that we are looking at? When the gravity of an object is intense enough, it can even bend light passing near it in a process called gravitational lensing. When the light rays bending around a massive object hit our eye, they don’t always synch back up into the single image that produced them. Instead, gravitational lensing can produce multiple image of the same object, which is perhaps my favorite effect in the cosmos.

Bending light around a massive object from a distant source. The orange arrows show the apparent position of the background source. The white arrows show the path of the light from the true position of the source.

While the physics behind gravitational lensing is complex, we more or less understand what is going on. In fact, Einstein himself used the phenomenon to corroborate his theory of general relativity.

When light misbehaves, it is always confusing. Having evolved brains that assume light moves in basically straight lines, we mistake the sky for pools of water in the desert and one galactic core becomes four.

Follow Blog by Email

About the Author

Kyle Hill is a science writer and communicator who specializes in finding the secret science in your favorite fandom. His work has appeared in Wired, The Boston Globe, Scientific American, Popular Science, Discover Magazine, and more. He is a TV correspondent for Al Jazeera America's science and technology show TechKnow.